Broken tool detector

ABSTRACT

A coolant and broken tool detecting circuit wherein the coolant for the tool is detected when the tool breaks. The circuit includes a supply nozzle for directing coolant against the tool and a receiver nozzle on the opposite side of the tool which receives coolant when the tool is broken. There is provided a diaphragm sensor communicating with the receiver nozzle for sensing pressure changes therein and indicating when the tool is broken, and there being also provided a supply of liquid to the receiver nozzle continuously for the purpose of purging the receiver nozzle of any contamination.

United States Patent [72] lnventor Richard F. Klem Wheaton,1ll. [21] App]. No. 820,094 [22] Filed Apr. 29,1969 [45] Patented Sept.28,1971 [73] Assignee lTElmperialCorporation 54 BROKEN Toot D ETEcToii #7 W V 7' 4 Claims, 1 Drawing Fig.

[52] U.S.Cl 408/16, 73/37, 239/71 [51] 1nt.Cl B23b 49/00, GOld 21/00 [50] Field of Search 73/37, 37.5, 37.6, 37.7, 37.8, 37.9; 239/71; 77/5.2

[56] References Cited UNlTED STATES PATENTS 2,065,702 12/1936 Hubbard 73/37.5 UX 3,240,410 3/1966 Jacobsen.. 73/37.7 X 7 3,243,993 4/1966 lacobse n BQLl a an Primary Examiner-Louis R. Prince Assistant Examiner-William A. Henry, ll Att0rneyHofgren, Wegner, Allen, Stellman & McCord ABSTRACT: A coolant and broken tool detecting circuit wherein the coolant for the tool is detected when the tool breaks. The circuit includes a supply nozzle for directing coolant against the tool and a receiver nozzle on the opposite side of the tool which receives coolant when the tool is broken, There is provided a diaphragm sensor communicating with the receiver nozzle for sensing pressure changes therein and indicating when the tool is broken, and there being also provided a supply of liquid to the receiver nozzle continuously for the purpose of purging the receiver nozzle of any contamination.

VENT

coounvr SUPPL Y al-I i BROKEN TOOL DETECTOR BACKGROUND OF THE PRESENT INVENTION It is conventional in machine tools to provide a hydraulic circuit for conveying filtered cooling oil to the tool itself for the purpose of preventing excessive tool heating during machining. It is also conventional in this art to provide a broken tool detecting circuit for the purpose of detecting a broken tool and shutting down the machine. One such broken tool detecting circuit includes a nozzle for directing an airstream against the tool and some means for detecting when the airstream becomes uninterrupted by a broken tool.

It is an object of the present invention to combine these two circuits into a single liquid hydraulic circuit employing the coolant liquid itself as the broken tool detecting fluid. This not only has the advantage of considerably simplifying the two circuits in their consolidation but also increases the reliability of the detecting circuits since in prior circuits where separate hydraulic and air circuits were provided, the cooling circuit frequently continued to interrupt the tool detecting airstream even after the tool was broken and thus provided a false readout permitting the continued operation of the machine. Where multiple workpieces are automatically transferred to such machine, the broken tool would damage the subsequent workpieces since the broken tool detecting circuit failed to shut down the machine upon tool breakage.

Another advantage in the consolidation of these functions is that the use of liquid in a detecting circuit, as opposed to air or another gas stream, is that the detector can operate over a much greater distance than possible with a gas stream.

SUMMARY OF THE PRESENT INVENTION In accordance with the present invention a coolant and broken part detecting circuit is provided that includes a supply nozzle for directing a coolant stream against a part and a receiver nozzle for receiving the coolant stream when the part does not interrupt it. A separate main cooling stream may also be provided when the circuit is used with a metal machining tool. A portion of the coolant supply fluid is also supplied to the receiver nozzle for the purpose of purging the receiver. A diaphragm operated sensor responsive to the pressure of fluid in the purging circuit provides an isolating interface to an air circuit which communicates with a conventional pressure to electric transducer. The output of the pressure to electric transducer may be connected, for example, to shut down the associated machine tool when the tool breaks. Another feature of the present device is that it is adaptable to circuits where remote sensing is required but where the physical size of the receiver assembly is too large for convenient mounting. Towards this end the receiver port may be positioned by suitable tubing to an appropriate position remote from the diaphragm sensor which detects changes in pressure in the purging stream discussed above. In this case, the purged stream will fill the diaphragm receptacle area, as well as the extension tubing and since the cooling liquid is essentially incompressible, the effect of an extension of the receiver by means of this tube between the diaphragm and the receiver nozzle is negligible. This, of course, reduces the size of the receiving mechanism at the point of the desired reception of the sensing stream.

A further advantage of the present invention is that because of the changes in air pressure level due to the deflection of the diaphragm sensor causing switching of sensitive switching elements which provide an output at predetermined pressure levels, very small changes in the liquid, momentum impinging on the receiver nozzle can be reliably detected and complete interruption of the detected liquid coolant stream is not necessary for reliable and repeatable actuation of the detecting means. Moreover, because of the integrating or averaging effect of the diaphragm sensor, minor variations in liquid pressure or quantitative liquid reaching this receiver are ignored, while retaining the basic snap action switching of the diaphragm sensor when the pressure level indicating broken tool is reached.

While the present invention is particularly useful in detecting the presence of a tool in a machine tool, it has other applications such as a parts detector in continuous process machine, where the distance through which the detecting stream must be projected is quite large or where, for other reasons, photoelectric or magnetic detection mechanisms are undesirable. Because of the inherent ruggedness of the present device and its self-cooling action, the sensor may be used in environments where the inherent high temperature precludes the use of other sensors.

BRIEF DESCRIPTION OF THE-DRAWING The drawing is a schematic illustration, partially in cross section of the present cooling and detecting circuit.

DETAILED DESCRIPTION OF THE PRESENT INVENTION Referring to the drawing, a machine tool such as drill 10 is shown in part without the associated machine tool for rotating and reciprocating the same. In its fully retracted position drill 10 does not go above line 11 so that the tool is in the path of the coolant in all of its positions unless the tool is broken.

The present circuit consists generally of a coolant supply 12, a supply nozzle 14, a receiver nozzle 16, a receiver block assembly 18, a pressure to electric transducer 20 and an air supply 22,

The coolant supply 12 supplies a relatively cool filtered liquid coolant to passage 28 and passage 29 to the supply nozzle 14. Supply nozzle 14 consists of a generally annular body member 32 having a central axial passage 33 communicating through a conical portion with a nozzle portion 35, threaded nuts 38 and 40 engage the body member 32 and define a means for fixing the nozzle in a suitable adjustable axial position with respect to a frame member positioned between the nuts 38 and 40. The nozzle member 32 is aligned so that coo Iant stream 44 emanating from nozzle 35 normally impinges on the tool 10. Moreover, the nozzle is positioned with respect to the range of movement of the tool such that the tool may not be retracted above the coolant stream 44 and is positioned so that it impinges on the tip of the tool when retracted. The coolant stream 44 is also referred to herein as the detected stream or flow. A main cooling stream directed against the workpiece may be provided, if desired, in addition to the detected stream.

Positioned opposite the supply nozzle 14 with respect to the tool 10 is a receiver nozzle 16 which includes a body member 48 having a central passage 49 therein communicating with an aligned nozzle portion 52 in turn communicating with a flared or conical receiver portion 54. Similar to the supply nozzle 14, the receiver nozzle 16 is provided with threaded nuts 58 and 60 for the purpose of fixing the receiver nozzle to a suitable frame member.

When the tool 10 breaks the detected liquid or coolant stream 44 is directed into the conical receiver portion 54 and increases pressure in the receiver nozzle. For the purpose of detecting this increase in pressure in the receiver nozzle. the receiver block assembly 18 is provided which may be remotely positioned with respect to the receiver nozzle 16 but communicating therewith through conduit 62. This permits the receiver block assembly 18 to be remotely positioned with respect to the nozzle 16 so that the space requirements for the circuit near the detecting area are minimized.

The receiver block assembly 18 includes a first member 64 having a recessed portion 66 therein facing a recessed portion 68 in a second member 69. The receiver members 64 and 69 are securely fastened together by suitable fasteners 70. Positioned between the recesses 66 and 68 is a diaphragm sensor 72 which separates the recesses into a liquid chamber 76 and an air chamber 78. The diaphragm sensor 72 acts as an isolating sensing element when it moves to the right closer to port when the pressure of fluid in chamber 76 exceeds the pressure of fluid in chamber 78. A vent port 84 communicates with chamber 78 and a control port 80' in member 64 communicates with chamber 76.

For the purpose of supplying fluid to the chamber 76 in the diaphragm sensor and for the purpose of supplying purging fluid to the coolant receiver nozzle 16, purging liquid supply passage 86 is provided which communicates with the main coolant supply conduit 28 through adjustable valve 87. The valve 87 is adjusted such that only a small portion of the coolant flow in line 28 passes to line 86 and exits through the coolant receiver nozzle 16 during normal operation.

Air is supplied from the constant pressure source 22 through line 90 and diaphragm sensor supply port 80 to chamber 78. This air normally vents through vent port 84. In normal operation the pressure in chamber 76 is approximately equal to that in chamber 78 so that the diaphragm 72 remains only slightly deflected to the right from its center position where supply port 80 is fully open and air vents through port 84 For the purpose of detecting closure of the diaphragm 72 against supply port 80, the pressure to electric transducer 20 communicates with the supply passage 90 through passage 92. Switch 20 consists of a body member 93 covered by an end cap 94 which holds an intermediate frame member 95 in position. Sandwiched between cap 94 and frame 95 is a diaphragm valve member 97 which defines a pressure chamber 98 communicating with the passage 92. Fixed to the frame member 95 is a microswitch 96 having conductors 99 connected thereto. The diaphragm 97 is positioned to depress plunger 100 of the microswitch 96 when pressure in lines 92 and 90 increases to the level which occurs when the diaphragm sensor member 72 restricts sufficiently port 80 upon broken tool detection.

While the operation of the present invention is believed obvious from the above description, the following operation of the device will summarize the present invention. During normal operation liquid coolant emanates from the supply nozzle 14 and impinges upon the tool for the purpose of cooling the tool. At the same time a small portion of liquid coolant is supplied to the receiver nozzle 16 through passage 86, passage 104, passage 105 and conduit 62 for the purpose of purging the receiver nozzle as well as the liquid side of the receiver block assembly 18. Air is supplied continuously from source 22 through line 90 to the diaphragm chamber 78 but under these conditions supply port 80 is opened so that the air vents through port 84 and a relatively low pressure condition exists in line 92 and the diaphragm chamber 98 associated with the pressure to electric transducer so that no electric output is provided from the transducer 20.

[n the event tool 10 breaks, the coolant stream 44 is directed into the receiver portion 54 causing an increase in pressure in the purging fluid in line 62 and in the diaphragm chamber 76. This causes the diaphragm 72 to deflect further to the right restricting the supply port 80 sufficiently to cause a rapid rise in pressure in air line 90 as well as air passage 92.

This in turn causes an increase in pressure in chamber 98 causing the diaphragm member 97 to be driven downwardly moving microswitch plunger 100 downwardly, thereby closing the microswitch and causing an electric output through line 99. This output may be utilized through suitable circuitry to terminate the operation of the machine tool associated with tool 10.

While the present invention is believed best applied in a broken tool detection and cooling circuit, it has other applications as well, such as in a parts cooling and detecting circuit.

lclaim:

1. A broken tool cooling and detecting circuit comprising: means for supplying liquid coolant under pressure, nozzle means communicating with said supply means and positioned to direct coolant against the tool, said nozzle means being spaced from the tool to provide a free stream of liquid coolant against the tool, receiver means aligned with said nozzle means for receiving said coolant when the tool does not interrupt coolant flow from the nozzle means, and means for detecting an increase in pressure in said receiver means and providing a signal indicating the failure of the tool to interrupt the coolant flow, said detecting means including a diaphra m operated sensor having a liquid chamber on one side of t e diaphragm and an air chamber on the other side of the diaphragm, means for supplying air to said air chamber, said liquid chamber communicating with said receiver means.

2. A broken tool cooling and detecting circuit as defined in claim 1, including a fluid pressure to electric transducer responsive to fluid pressure in said air chamber.

3. A broken tool cooling and detecting circuit as defined in claim 2, said air supply means communicating with both said pressure to electric transducer and said air chamber of said detecting means.

4. A broken tool detection and tool cooling circuit, com prising: means for supplying liquid coolant under pressure, supply nozzle means communicating with said supply means for directing supply liquid toward said tool to cool said tool, said supply nozzle means being spaced from said tool to provide a free stream of coolant against said tool, receiver noule means positioned to receive supply liquid from said supply nozzle means when the tool is broken, means for supplying a minor portion of said supply liquid to said receiver nozzle to minimize contamination thereof, a diaphragm sensor for detecting a broken tool condition including a liquid chamber and an air chamber, said liquid chamber communicating with said means for supplying a minor portion of coolant to said receiver nozzle means so that the diaphragm sensor responds to pressure changes in the latter coolant, means for supplying air to said diaphragm sensor in an air chamber in opposition to the coolant in the liquid chamber, and an electric transducer in said air supply means for providing an electric signal when the tool is broken. 

1. A broken tool cooling and detecting circuit comprising: means for supplying liquid coolant under pressure, nozzle means communicating with said supply means and positioned to direct coolant against the tool, said nozzle means being spaced from the tool to provide a free stream of liquid coolant against the tool, receiver means aligned with said nozzle means for receiving said coolant when the tool does not interrupt coolant flow from the nozzle means, and means for detecting an increase in pressure in said receiver means and providing a signal indicating the failure of the tool to interrupt the coolant flow, said detecting means including a diaphragm operated sensor having a liquid chamber on one side of the diaphragm and an air chamber on the other side of the diaphragm, means for supplying air to said air chamber, said liquid chamber communicating with said receiver means.
 2. A broken tool cooling and detecting circuit as defined in claim 1, including a fluid pressure to electric transducer responsive to fluid pressure in said air chamber.
 3. A broken tool cooling and detecting circuit as defined in claim 2, said air supply means communicating with both said pressure to electric transducer and said air chamber of said detecting means.
 4. A broken tool detection and tool cooling circuit, comprising: means for supplying liquid coolant under pressure, supply nozzle means communicating with said supply means for directing supply liquid toward said tool to cool said tool, said supply nozzle means being spaced from said tool to provide a free stream of coolant against said tool, receiver nozzle means positioned to receive supply liquid from said supply nozzle means when the tool is broken, means for supplying a minor portion of said supply liquid to said receiver nozzle to minimize contamination thereof, a diaphragm sensor for detecting a broken tool condition including a liquid chamber and an air chamber, said liquid chamber communicating with said means for supplying a minor portion of coolant to said receiver nozzle means so that the diaphragm sensor responds to pressure changes in the latter coolant, means for supplying air to said diaphragm sensor in an air chamber in opposition to the coolant in the liquid chamber, and an electric transducer in said air supply means for providing an electric signal when the tool is broken. 